Statistical Approach for An analysis for SARS-CoV-2 viral load by patient age
"To look for relationships between viral load and age, we took two approaches: 1) testing for statistical differences between the viral loads in aggregated age categories, and 2) treating age as a continuous variable and using a gamma regression to predict viral load. In the age categorization we made comparisons between three groups of patients: a) 0-9 years versus 10-99 years, b) 0-9 years versus 19-99 years, and c) 0-19 years versus 20-99 years. Age category viral loads were compared via the Mann-Whitney rank test and Welch’s t-test. The categories were also examined via a Bayesian analysis using gamma mixture models to account for the multi-modal nature of the viral load data. The Bayesian analysis used a mixture of three gamma distributions and accounted for variations between age groups by estimating age-group specific component weights. To provide a fine-grained overview of the data, log10 viral loads for an overall 10-year age bracket breakdown, with number and percentage of RT-PCR positive patients are shown in Table 2, while Figures 4 and 5 show the distribution of viral load values in these groups."
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Statistical Approach for An analysis for SARS-CoV-2 viral load by patient age
Figure 1: Utilization of LC480 and cobas test systems over the study period for An analysis of SARS-CoV-2 viral load by patient age
Figure 2: Differences in viral load in an exemplary group of patients aged 0-11 years with and without a pre-existing condition.
Figure 3: Viral loads over time in children from A) 0-9 and B) 0-19 year olds.
Figure 4. Distribution of viral loads by age group and PCR instrument.
Figure 5: Viral load by patient 10-year age strata.
Figure 6: Conditional effect of age from a Bayesian gamma regression predicting viral load from age, while adjusting for type of PCR system (LC480 or cobas).